The Clinical Core is an essential element of the Gene Therapy Center and will be the focus of all clinical activities involving patients. Patients currently enrolled in the Johns Hopkins Hospital Cystic Fibrosis Center will be invited to participate in the cystic fibrosis gene therapy protocol. Patients taking part in the gene therapy protocol will be hospitalized in the General Clinical Research Center (GCRC) and all outpatient follow-up clinical evaluations will be carried out in the GCRC. All laboratory, radiographic and imaging studies will be coordinated through the Clinical Core. Specimens for laboratory evaluations including respiratory tract secretions, blood, and bronchoalveolar lavage fluid will be obtained and processed in the GCRC. Pulmonary function testing will be carried out in the GCRC by Center staff and all nasal brushings, transepithelial potential difference measurements and bronchoscopies will be performed in the GCRC by Clinical Core staff. The services of the GCRC staff, which include a senior research nurse and pediatric nutritionist, will be available to patients enrolled in the gene therapy protocol. In addition, harvesting of bone marrow for preparation of cell lines will take place through the Clinical Core in the GCRC.